1. Field of the Invention
This invention relates to closure devices for pipes, and in particular to an expandable closure device adapted for placement in a pipe opening in sealing relation.
2. Description of the Prior Art
Closure devices or plugs are used in a wide variety of applications for closing openings in pipes and the like. Exemplary uses in the plumbing field include closing and sealing the open ends of sewer, drain waste and vent pipes. It is frequently desirable that such closure devices or plugs be removable and reusable. For example, in the construction of sewer lines, sewer mains are typically installed sometime prior to the connection of lateral sewer lines to individual structures. Connections which are not needed are typically plugged with removable closure devices until laterals are run therefrom to new structures. However, before being placed in service, all of the connections must be plugged to allow the connected laterals and the rest of the sewer system to properly function. Also, the entire sewer system must be closed so that it may be pressure tested for leaks. Such closure devices must therefore be capable of withstanding the pressures associated with normal operation of the rest of the sewer system and with an air or water pressure test. For example, water test pressures of approximately 4.3 psi (about 10 feet of water head) are commonly specified for these types of systems.
Removable pipe closure devices are also extensively used as "clean out" plugs. These are normally provided at pedetermined locations in waste and drain piping systems for providing access thereto. Such clean out plugs are removed to dislodge and extract blockages from the system.
A variety of closure devices and plugs have previously been designed in an attempt to achieve a plug which is relatively inexpensive, easy to install and remove, and capable of withstanding relatively high pressures. For example, it is well known to provide a coupling having female threads on the end of a pipe and to threadably insert a plug having male threads to close the pipe. A seal may be effected in such devices by either tapering the threaded portions of the coupling and the plug (e.g. using standard NPT tapered threads) or by using an elastomeric gasket which seats between the plug and the coupling. However, this method is not practiced on pipes comprising certain materials, for example, clay.
Plastic pipes comprising, for example, acrylonitrile-butadiene-styrene (ABS) and polyvinyl chloride (PVC) may be closed by solvent welding a plug on their open ends. However, the end of the pipe must be cut off to open it, thus making this method undesirable for clean outs. Plastic ABS and PVC fittings having tabs extending from the sockets or hubs for receiving clean out plugs are also known. In such systems, inclined slots on the clean out plug receive the tabs whereby a seal is effected when the plug is twisted. A disadvantage with this system is that both elements, that is the fitting and the plug, must match.
A major drawback to the use of all of the aforementioned systems relates to their lack of uniformity and interchangeability. Thus, plumbers and their suppliers must stock pipe stopper parts of not only different sizes, but also of different types. Therefore, removable plugs have been devised which are capable of effecting a frictional sealing engagement with the bore of a "plain end" pipe having a smooth surface. For example, the Roberts et al U.S. Pat. No. 3,307,732 discloses a plug having a tapered surface for tightly compressing a sealing ring into engagement with the inside of a pipe as the plug is pulled outwardly by the installer or forced outwardly by internal pressure. However, the sealing ring forms a relatively narrow seal for closing the pipe, and special tools are required for removing the device.
The Jackson U.S. Pat. No. 3,494,504 also shows a device for forcing a sealing ring into engagement with the inside of a pipe. However, that device has several interconnecting parts requiring manufacture to relatively exact tolerances and thus necessitates a relatively high cost. A further type of closure device for a plumbing clean out fitting is disclosed in the Polster et al U.S. Pat. No. 3,993,102 wherein a male threaded plug compresses a gasket into engagement with a body having a female threaded portion. However, the body is placed on the outside of a pipe end and requires caulking to form a tight seal with respect thereto, and is thus not particularly suitable for removal and reuse. Therefore prior art fittings and plugs have tended to be complex, not interchangeable or not well adapted for easy installation, removal and reuse.
In the practice of the present invention, a sealing ring is provided having a tapered bore therethrough with rounded threads. A tapered plug having corresponding rounded threads is threadably engageable in the sealing ring bore. The sealing ring is placed in an opening in a pipe and the like and expands into sealing engagement therewith as the plug is axially advanced into the sealing ring bore. The rounded threads of the sealing ring bore and the plug function to prevent the plug, which generally comprises a harder material than the sealing ring, from cutting into the elastomeric sealing ring. A multi-sided boss is integrally attached to an outer end of the plug whereby the plug may be installed or removed with a wrench.
A peripheral surface of the sealing ring frictionally engages an inside surface of the pipe opening whereby relative rotation and axial sliding therebetween is prevented as the plug is inserted or withdrawn.
The principal objects of the present invention are: to provide a closure device for openings in pipes and the like comprising a variety of materials; to provide such a closure device for female pipe ends having bells, sockets or hubs and plain male pipe ends; to provide such a closure device which may be positioned inside either the bore or hub of a female pipe end; to provide such a closure device which is easily installed and removed; to provide such a closure device which is reusable; to provide such a closure device which provides a relatively large area of sealing contact with the inside surface of a pipe; to provide such a closure device which forms a sealing engagement with either a smooth or threaded inside surface of a pipe; to provide such a closure device with a sealing ring peripheral surface which frictionally engages a pipe opening inside surface and thereby prevents relative rotation or axial sliding therebetween as the plug is inserted or withdrawn; to provide such a closure device with corresponding rounded threads on a sealing ring bore and a plug; to provide such a closure device which may be installed and removed with a common hand tool; to provide such a closure device capable of withstanding relatively high pressures; and to provide such a closure device which is economical to manufacture, efficient in use, capable of a long operating life, and particularly well adapted for the proposed use.
Other objects and advantages of this invention will become apparent from the following description taken in conjunction with the accompanying drawings wherein are set forth, by way of illustration and example, certain embodiments of this invention.
The drawings constitute a part of this specification and include exemplary embodiments of the present invention and illustrate various objects and features thereof.